Apparatus for producing single crystals

Abstract

This invention relates to the apparatus and the process for producing single crystals with little OSF generation and excellent dielectric strength of gate oxide films by adjusting the temperature gradient of the silicon single crystal in the direction of pulling. The apparatus is provided with a crucible which contains the melt of the single crystal material, a heating element which heats the melt, a pulling shaft to grow the single crystal, a protective gas inlet pipe, and a chamber which contains all above mentioned components. In addition, the apparatus is provided with a circular cylinder or a cylindrical shaped heat resistant and heat insulating component below the protective gas inlet pipe noted above. In the process of producing single crystals, the single crystal is pulled up through the circular cylinder or a cylindrical shape heat resistant and heat insulating component below the protective gas inlet pipe, and while the palled-up crystal is at high temperature the temperature gradient in it is held small and when the crystal is cooled to low temperature the temperature gradient is increased.

What is claimed is: 
     
       1. An apparatus for producing single crystals comprising: a chamber containing a crucible for containing a melt from which a single crystal is grown, a heating element for heating the melt, and a pulling mechanism for growing the single crystal after contacting the melt with a seed crystal;   a protective gas inlet pipe arranged to release heat by thermal conduction with the chamber, the protective gas inlet pipe extending downwardly into the chamber and surrounding the pulling mechanism, supporting components installed at intervals, on a lower end of the protective gas inlet pipe, and a heat resistant and heat insulating component supported on the lower end of the protective gas inlet pipe by the supporting components, the heat resistant and heat insulating component surrounding a pulling zone of the single crystal and a lower end of the heat resistant and heat insulating component being above the melt in the crucible, the heat resistant and heat insulating component providing a small temperature gradient and the protective gas inlet pipe providing a high temperature gradient in the single crystal.   
     
     
       2. The apparatus for producing single crystals described in claim 1, the protective gas inlet pipe having an inner surface which is maintained at a low temperature by heat dissipation to the chamber, heat dissipation from the heat resistant and heat insulating component to the protective gas inlet pipe being minimized by the supporting components, and the heat resistant and heat insulating component having an inner surface which is maintained at a high temperature as a result of heat from a melt in the crucible and heat from the heating element. 
     
     
       3. The apparatus for producing single crystals described in claim 1, wherein the heat resistant and heat insulating component maintains the small temperature gradient in a lower portion of the single crystal surrounded by the heat resistant and heat insulating component, the lower portion being at a temperature above 1250° C., and the protective gas inlet pipe maintains the high temperature gradient in an upper portion of the single crystal surrounded by the protective gas inlet pipe, the upper portion being at a temperature between 900° C.-1100° C. 
     
     
       4. The apparatus for producing single crystals described in claim 1, wherein the heat resistant and heat insulating component is cylindrical or conically narrowing downward. 
     
     
       5. The apparatus for producing single crystals described in claim 1, wherein the heat resistant and heat insulating component is made of graphite. 
     
     
       6. The apparatus for producing single crystals described in claim 1, wherein the heat resistant and heat insulating component is coated with silicon carbide. 
     
     
       7. The apparatus for producing single crystals described in claim 1, wherein the protective gas inlet pipe includes a lifting mechanism which raises and lowers the protective gas inlet pipe. 
     
     
       8. The apparatus for producing single crystals described in claim 1, wherein the supporting components are replaceable with other supporting components to allow adjustment of a distance extending vertically between an outlet of the protective gas inlet pipe and an inlet of the heat resistant and heat insulating component. 
     
     
       9. The apparatus for producing single crystals described in claim 1, wherein argon gas is blown through the protective gas inlet pipe at a constant rate. 
     
     
       10. The apparatus for producing single crystals described in claim 1, wherein the crucible contains a melt of silicon and the pulling mechanism is supporting a silicon single crystal. 
     
     
       11. The apparatus for producing single crystals described in claim 1, wherein the supporting components comprise a plurality of circumferentially spaced-apart components extending between an outer periphery of the protective gas inlet pipe and an upper end of the heat resistant and heat insulating component. 
     
     
       12. The apparatus for producing single crystals described in claim 1, wherein an upper end of the heat resistant and heat insulating component is spaced vertically below the lower end of the protective gas inlet pipe.